The present invention relates to inks with improved flow (or rheology) characteristics. More specifically, the invention relates to flow-modifying agents for solvent-based and water-based inks consisting of the metal salts of aromatic hydroxy carboxylic acids and aromatic carboxylic acids.
Organic pigments have achieved great importance in the graphic art industry due to their tinctorial strength, brilliance, purity of shade and high transparency. Their tinctorial strength is due to the fact that the pigment particles have a large surface area, which is due to the small particle size of the pigment molecules. This same feature brings about physical chemical interaction of the pigments with the solvents and binders used during the manufacture of the printing inks in which relatively stable gel structures having correspondingly unfavorable rheological properties are formed. Poor rheological properties, for example, thick and thixotropic dispersions, are generally assumed to be related to flocculation of pigment particles.
In addition to poor rheology, flocculation causes a loss of gloss and color strength during the grinding stage in the preparation of inks and paint, and causes the dispersion (which includes the ink vehicle and the pigment dispersed therein) to become very thick and thixotropic thereby making the formulations difficult to handle. Formulations that are easier to work can be obtained by decreasing the pigment content but this obviously affects the through-put of ink for a given grinding capacity. This disadvantage has been disclosed several times in the art, for example by F. M. Smith in Paint Manufacture, August 1957, page 256 and G. Wormald in Paint and Varnish Products, April 1957, page 56.
There has been a growing tendency in the graphic arts industry towards the development of high-speed printing machines which require printing inks having high tinctorial strengths and very good flow properties for multi-color printing. For example, British Patent 1,138,465 relates to the addition of compounds containing basic groups. British Patent 1,339,068 discloses the acid derivatives of pigments. German Patent 1,155,755 teaches the after treatment of pigments with organic solvents. British Patent 1,356,254 discloses water-soluble dyes. U.S. Pat. No. 4,468,255 discloses pigment derivatives to improve rheology. British Patent 1,566,803 discloses ammonium salts of colored acids.
As used herein the term solvent refers to a volatile material, usually a liquid, that is capable of dissolving another substance, usually a solid to form a solution. In ink manufacturing, solvents are used to dissolve materials in the ink vehicle, let down (or reduce) the viscosity of the reactive vehicle, and assist in the blending of the vehicle and pigments. The term solvent as used herein does not include water or aqueous-based carriers or additives.
In the past, attempts to solve the problems associated with ink having poor rheological properties have primarily involved the addition of surfactants to improve the dispersibility of organic pigments in water-based ink carriers. Further, surfactants can cause undesirable properties in the dried ink. For example, dried ink that includes surfactants is usually more prone to running or smudging when it comes into contact with water.
The present inventor has discovered that the metal salts of aromatic hydroxy carboxylic acids or aromatic carboxylic acids, which are used as negative charge control agents in electro-photography, when added to organic pigments, lower the viscosity and improve the flow of water-based and solvent-based inks. The improved ink disclosed herein can utilize monoazo yellow or orange pigments, disazo pigments, xcex2naphthol and naphthol AS based pigments. Other pigments that may be used in the practice of the invention include: azo pigment lakes, benzimidazolones, disazo condensation pigments, metal complex, phthalocyanine blues and greens, quinacridones and other polycyclic pigments, basic dye toners, and others all of which are described in Industrial Organic Pigments by Herbst and Hunger.
To solve the problems with the prior art the present invention comprises (1) an ink vehicle, which is either solvent-based or aqueous-based, (2) a pigment, and (3) a flow-modifying agent, which is a metal salt of an aromatic carboxylic acid or an aromatic hydroxy carboxylic acid. The invention is also directed to a pigment for use in printing inks wherein the pigment includes a flow-modifying agent according to the invention.
The present invention comprises (1) an ink vehicle, which can be either water-based or solvent-based, (2) a pigment, which is preferably an organic pigment and most preferably an azo pigment, and (3) a flow-modifying agent, which is a metal salt of an aromatic carboxylic acid or an aromatic hydroxy carboxylic acid. The improved pigments of the present invention may be used in inks or paints. With regards to inks, some respective formulations are disclosed in: R. H. Leach, editor, The Printing Ink Manual, Fourth Edition, Van Nostrand Reinhold (International) Co. Ltd., London (1988), particularly pages 282-591; and with regard to paints some formulations are disclosed in: C. H. Hare, Protective Coatings, Technology Publishing Co., Pittsburgh (1994), particularly pages 63-288. The foregoing references are hereby incorporated by reference herein for their teachings of ink and paint compositions, formulations and vehicles which may be utilized in the practice of this invention.
The improved ink disclosed herein can utilize any organic pigment. Organic pigments that may be used in practicing the invention are azo pigments (including monoazo pigments and disazo pigments), xcex2-naphthol pigments, naphthol AS pigments, azo pigment lakes, benzimidazolone pigments, metal complex pigments, isoindolinone pigments, isoindoline pigments, polycyclic pigments, phthalocyanine pigments, quinacridone pigments, perylene pigments, perinone pigments, diketopyrrolo pyrrole (DPP) pigments, thioindigo pigments, anthrapyrimidine pigments, flavanthrone pigments, pyranthrone pigments, anthanthrone pigments, dioxazine pigments, triarylcarbonium pigments, and quinophthalone pigments. The molecular structures and the process for making these pigments are known to those skilled in the art. Such pigments are described in one or more of the following references: W. Herbst, K. Hunger, Industrial Organic Pigments, 2d (1997), P. F. Gordon, P. Gregory, Organic Chemistry In Color (Springer-Verlog 1982); H. Zollinger, Color Chemistry (VCH Verlegseselschaft MBH 1987); P. Gregory, High-Technology Applications of Organic Colorants (Plenum Press 1991); and J. Griffiths, Colour and Constitution of Organic Molecules (Academic Press 1976), the disclosures of which are incorporated herein by reference. Azo pigment preparations and their method of manufacture are also disclosed in U.S. Pat. No. 3,759,733; U.S. Pat. No. 3,725,101; U.S. Pat. No. 3,759,731; U.S. Pat. No. 3,775,148; U.S. Pat. No. 4,474,609; U.S. Pat. No. 4,720,304; U.S. Pat. No. 4,946,508; and U.S. Pat. No. 5,591,257, and a United States patent application Ser. No. 09/185,931 filed on Nov. 4, 1998, now U.S. Pat. No. 6,136,087 entitled Crystal Growth Inhibitor, the respective disclosures of which are incorporated herein by reference.
Virtually any metal and any aromatic hydroxy carboxylic acid or aromatic carboxylic acid can be used in the practice of the invention as long as the acid contains at least one aromatic molecule. Some metal salts that can be used in the practice of the invention, and their method of manufacture, are disclosed in the following U.S. Patents, the disclosures of which are incorporated herein by reference: U.S. Pat. No. 4,404,271; U.S. Pat. No. 4,407,924; U.S. Pat. No. 4,656,112; U.S. Pat. No. 5,143,809; U.S. Pat. No. 5,223,368; U.S. Pat. No. 5,393,632; and U.S. Pat. No. 5,403,690.
It will be appreciated that a metal salt of the present invention may include more than one metal and/or more than one acid group. If more than one acid group is included, the invention may include either a symmetrical metal complex wherein two identical acid groups are used or an asymmetrical complex wherein two different acid groups are used.
Generally, substituted or unsubstituted aromatic acids are preferred, such as salicylic acid, naphtoic acid, and painoic acid. These may be substituted with any molecule including an alkyl or an aralkyl group or an aliphatic carbon chain. Depending upon the valence of the metal used, an acid group is selected that has a corresponding counter ion.
Examples of useful acid groups for forming the metal salts of the invention are 2-hydroxy-3-naphthoic acid; alkyl (C4-C9)-2-hydroxy-3-naphthoic acid; 5,6,7,8-tetrahydro-2-hydroxy-3-naphthoic acid; alkyl (C4-C9)-5,6,7,8-tetrahydro-2-hydroxy-3-naphthoic acid; 1-hydroxy-2-naphthoic acid; alkyl (C4-C9)-1-hydroxy-2-naphthoic acid; 5,6,7,8-tetrahydro-1-hydroxy-2-naphthoic acid; alkyl (C4-C9)-salicylic acid; 3,5-dialkyl (C4-C9)-salicylic acid; 2-hydroxy-3-naphthoic acid; alkyl (C4-C9)-2-hydroxy-3-naphthoic acid; 5,6,7,8-tetrahydro-2-hydroxy-3-naphthoic acid; alkyl (C4-C9)-5,6,7,8-tetrahydro-2-hydroxy-3-naphthoic acid; 1-hydroxy-2-naphthoic acid; alkyl (C4-C9)-1-hydroxy-2-naphthoic acid; 5,6,7,8-tetrahydro-1-hydroxy-2-naphthoic acid; hydroxy bis[3,5-tertiary butyl salicylic]aluainate; hydroxy bis [3,5-tertiary butyl salicylic]alurniinate mono-, di-, tri-or tetrahydrates; hydroxy bis[salicylic]aluminate; hydroxy bis[monoalkyl salicylic]aluminate; hydroxy bis[dialkyl salicylic]aluminate; hydroxy bis[trialkyl salicylic]aluminate; hydroxy bis[tetraalkyl salicylic]aluminate; hydroxy bis[hydroxy naphthoic acid]aluminate; hydroxy bis[monoalkylated hydroxy naphthoic acid]aluminate; bis[dialkylated hydroxy naphthoic acid]aluminate wherein alkyl preferably contains 1 to about 6 carbon atoms; bis[trialkylated hydroxy naphthoic acid]aluminate wherein alkyl preferably contains 1 to about 6 carbon atoms; bis[tetraalkylated hydroxy naphthoic acid]aluminate wherein alkyl preferably contains 1 to about 6 carbon atoms; bis(3,5-di-tertiary-butyl salicto) manganese, bis(3,5-di-isopropyl salicto) manganese, and bis(3,5-methoxy salicto) manganese; alkyl(C4-C9)salicylic acids; 3,5-dialkyl(C4-C9)salicylic acids, 2-hydroxy-3-naphthoic acid; alkyl(C4-C9)-2-hydroxy-3-naphthoic acids; 5,6,7,8-tetrahalogen-2-hydroxy-3-naphthoic acids, salicylic acid; alkyl(C1-C12) salicylic acid; 3,5-dialkyl(C1-C12) salicylic acid; 1-hydroxy-2-naphthoic acid; 2-hydroxy-3-naphthoic acid; 2-hydroxy-1-naphthoic acid; alkyl(C3-C12)-hydroxy-3-naphthoic acid; 6-(alpha-methylbenzyl)-2-hydroxy-3-naphthoic acid; n-dodecenyl succinic acid; isododecenyl succinic acid; n-dodecyl succinic acid; isododecyl succinic acid; isooctyl succinic acid; n-octyl succinic acid; n-butyl succinic acid; and the esters thereof; maleic acid; fumaric acid; mesaconic acid; citraconic acid; itaconic acid; glutaconic acid; phthalic acid; isophthalic acid; terephthalic acid; cyclohexanedicarboxylic acid; succinic acid; adipic acid; sebacic acid; malonic acid; a dimer of linolenic acid; and the lower alkyl esters thereof; 1,2,4-benzenetricarboxylic acid; 1,2,5-benzenetricarboxylic acid; 1,2,4-cyclohexanetricarboxylic acid; 2,5,7-naphthalenetricarboxylic acid; 1,2,4-naphthalenetricarboxylic acid; 1,2,4-butanetricarboxylic acid; 1,2,5-hexanetricarboxylic acid; 1,3-dicarboxy-2-methylcarboxy propene, 1,3-dicarboxy-2-methyl-2-methylcarboxy-propanetetra (methylenecarboxy) methane, enpol trimeric acid; and the anhydrides thereof.
As previously stated, virtually any metal having the proper valence may be used to bond with the acid group to create a metal salt and form a flow-modifying agent in accordance with the invention. Series IA metals that may be used are sodium, potassium, rubidium, cesium, and francium; series IIA metals that may be used are beryllium, magnesium, calcium, strontium, and barium; series IIIA metals that may be used are scandium, yttrium, lanthanum and actinium; series IVA metals that may be used are titanium and zirconium; series VA metals that may be used are vanadium, niobium and tantalum; series VIA metals that may be used are chromium, molybdenum, and tungsten; series VIIA metals that may be used are manganese, technetium and rhenium; series VIIIA metals that may be used are iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium and platinum; series IB metals that may be used are copper, silver and gold; series IIB metals that may be used are zinc and cadmium; series IIIB metals that may be used are gallium, indium and thallium series IVB metals that may be used are silicon, germanium, tin lead; series VB metals that may be used are arsenic, antimony and bismuth; series VIB metals that may be used are selenium, tellurium and polonium.